This invention relates to magnetic heads and in particular to methods of forming magnetic heads with narrow pole widths.
A typical inductive thin film magnetic magnetic head comprises a first magnetic pole layer and a second magnetic pole layer with an electrical coil between the two pole layers. The two pole layers contact each other at one end at a back closure to form a continuous magnetic path, with a narrow transducing gap at the other end. The portions of the first and second poles separated by the transducing gap are designated respectively as the first and second pole tips. In order to write data with narrow track widths and high linear recording densities, it is necessary to provide a magnetic head with narrow pole tips. However, there are technical problems associated with fabricating a magnetic head with narrow pole tips. A key problem confronted during manufacture is the alignment of the two pole tips. Various methods have been suggested to solve this problem.
FIG. 1 shows a prior art approach in which a magnetic head 2 is fabricated with a first pole tip 4 wider in lateral dimension than a second pole tip 6. The wider first pole tip 4 tolerates a certain degree of misalignment during the laying of the second pole tip 6. The width of the second pole tip TW is intended to, define the track width of the magnetic head 2. However, the problem with this approach is that due to the larger width of the first pole tip 4, magnetic flux fringing beyond the width of the second pole tip 6 is unavoidable. The fringing flux, such as flux lines F emanating from the second pole 6 to the first pole 4 as shown in FIG. 1A, would result in registering a data track 7 with a width W having ambiguous track boundaries. This seriously limits the track-to-track separations on the recording medium 8.
U.S. Pat. No. 4,947,541, Toyoda et al., entitled. xe2x80x9cMethod For Producing a Thin Film Headxe2x80x9d, issued Aug. 14, 1990, describes a magnetic head with a sloped side wall for the second pole tip in an effort to reduce fringing flux lines. As shown in FIG. 2 herein, the magnetic head 10 includes a first pole 12 and a second pole 14 separated by a gap layer 16. The second pole 14 has sloped side wall surface 14A and 14B which diverge away from the first pole tip 12. The sloped side walls 14A and 14B reduce fringing flux between the first and second pole tips 12 and 14 as illustrated by the lower number of flux lines F as shown in FIG. 1B. Nevertheless, fringing flux still exists and the resultant track width W registered on the medium surface 8 remains ambiguous.
Magnetic heads with vertically aligned sidewall pole tips have been described, as in U.S. Pat. No. 5,285,340, Ju et al., entitled xe2x80x9cThin Film Magnetic Head with Conformable Pole Tipsxe2x80x9d, issued Feb. 8, 1994. FIG. 3 shows a magnetic head 18 having vertically aligned side walls for both the first and second pole tips 20, 22 relative to first and second yoke layers 24 and 26, respectively. With the aligned side walls for the first and second pole tips 20 and 22, the magnetic head 18 can provide better defined data track width W in comparison with the magnetic heads 2 and 10 shown in FIGS. 1 and 2. The aligned first and second pole tips 20 and 22 are made available through a number of intermediate xe2x80x9cstitchingxe2x80x9d steps to the respective first and second yoke layers 24 and 26. Specifically, in between the pole tip layers 22 and 20, buffering layers must be interposed in order to maintain magnetic continuity. The intermediate steps incur additional costs of manufacturing.
Storage products, such as disk drives, are now fabricated with relatively small physical sizes and with increased storage capacities. As a consequence, data tracks on the media are registered with much narrower widths and higher linear recording densities. Data tracks written with ambiguous track boundaries seriously affect track-to-track separation, which in turn adversely affects storage capacity. Accordingly, it is desirable to provide magnetic heads capable of writing data tracks with well defined track boundaries, and at reasonable manufacturing costs.
It is an object of the invention to provide a magnetic head capable of writing narrow data tracks with high linear recording densities.
It is another object of the invention to provide a magnetic head that affords simplicity of fabrication and with reduced manufacturing cost.
In accordance with the invention, a magnetic head is formed with a stack of layers on a substrate. The stack of layers includes a nonmagnetic gap layer sanwiched between a first pole layer, which is disposed atop the substrate, and a sacrificial layer which is preferably made of a metal. A protective layer, such as alumina (Al2O3), is then deposited over and around the stack of layers. After planarization and ion milling, the sacrificial layer is, exposed. The sacrificial layer is thereafter etched away leaving a volume of space in the protective layer and above the nonmagnetic gap layer. After the deposition of an inductive coil with the associated dielectric layers, a second pole layer is then laid with the pole tip deposited in the volume of space, resulting in the first and second pole tips having vertically aligned side walls. With the vertically aligned side walls, the side fringing flux of one pole tip to another is substantially reduced resulting in a magnetic head capable of writing data tracks with well defined boundaries during normal operations.